This invention relates to a process for preparing particles of polymer, e.g., spheroidal particulates or beads of the bioabsorbable variety, employing various individual atomization techniques such as melt extrusion and/or rotary atomization. The particles are useful, inter alia, in the repair of damaged or defective bone.
The medical use of polymer particles including those of the bioabsorbable variety are known, inter alia, from U.S. Pat. Nos. 3,882,858; 4,535,485; 4,547,390; 4,643,735; and 4,663,447. There has been an increase in interest in utilizing both bioabsorbable and non-absorbable particles to facilitate bone or fibrous tissue repair/reconstruction.
A number of processes are known for preparing finely divided polymeric particles, e.g., mechanical grinding, solvent precipitation, dispersion, and spray atomization of solutions or slurries. U.S. patent application Ser. No. 654,219, filed Feb. 12, 1991, now U.S. Pat. No. 5,143,662 describes producing particles of polymer by subjecting the polymer to rotary atomization. In rotary atomization, the polymer is applied to a rotation bell, cup or disk with mechanical forces predominating in the breakup of the polymer into particles. U.S. patent application Ser. No. 503,264, filed Apr. 2, 1990 and now U.S. Pat. No. 5,102,983 issued Apr. 7, 1992 describes a process for preparing foamed, bioabsorbable polymer particles by a freeze-drying technique.
Processes which form microspheres of absorbable material less than or equal to 0.2 mm in diameter for use in controlled release of drugs, are well-known. Such spheres have generally been formed by a solvent evaporation technique. Alternatively, polymeric microspheres, e.g., beads, of average particle size greater than or equal to 0.2 mm in diameter can be formed by an emulsion polymerization process. Such emulsion polymerization has been successfully utilized to form beads of polymethylmethacrylate and styrene.
For medical applications, it is often desirable to control not only the particle size distribution of the polymeric particles but level of fibers which are present as well.